A convenient and inexpensive manner in which large quantities of data and information can be stored is by reducing the size of the original material. One commonly used method of storing reduced size materials is by copying them onto strips of microfilm which after processing, can be wound onto a reel for compact storage.
It is common practice with standard size documents to use an automatic rotary-type microfilm camera wherein the documents are fed automatically and filmed as they pass through the machine. It is a conventional practice primarily for convenience that light-tight film cassettes are used with this type of microfilming device. Standard unexposed film reels as received from the manufacturer are loaded into reusable film cassettes in a darkroom and are properly threaded through appropriate rollers to a take-up roll. The cassette is then closed with a light-tight cover. The cassette may then be carried into a light area and loaded into a machine and removed at any time without any danger of exposing the film contained therein. In fact, it is common practice to film a number of documents that would constitute a job or a run that would cause only a limited amount of the film in the cassette to be exposed. The cassette could then conveniently be removed from the camera until more documents associated with that job could be accumulated for filming. In the meantime, another cassette could be inserted in the microfilm camera to perform entirely different filming operations and in fact, may be exposed using a different format.
One format commonly used in microfilming is known as "duo" filming; that is, where images are placed along one lateral half of the film while it is moving in one direction and the other lateral half of the film is exposed during motion in the opposite direction. However, this normally required that the cassette be removed from the machine and taken to a darkroom where the cover was removed and the now full takeup reel be turned over, exchanging places with the empty supply reel. With the film once again properly threaded in the cassette, the cassette may be returned to the machine so that the remaining lateral half of the film could be exposed.
One object of the present invention is to provide a cassette having a bi-directional film transport and dual imaging ports, thereby allowing duo filming without requiring the re-loading of the cassette as in the past.
Another object of the present invention is the provision that the film reels within the cassette be in symmetrical relation to a diagonal plane, containing an axis of symmetry, extending between the reels and bisecting the corner of the cassette with two exposure windows adjacent the corner and at respective opposite sides thereof in symmetrical relation to the diagonal plane extending between the reels. This allows the first side of the film to be exposed and the cassette may then be rotated about its axis of symmetry and reloaded into its original drive location so that the second half of the film may now be exposed through the second image port.
The cassette is also configured to support a dual filming system where two rolls of film are exposed simultaneously. With such a system, two film drives could be used with one cassette for example, placed above another with each cassette being loaded into respective film chambers. Such an arrangement was commonly used if the film mode was either simplex or duplex so that two identically exposed rolls of film were provided, and after processing, a working roll and a backup or archival roll was created. As mentioned earlier, additional problems were encountered if the duo or duo-duplex modes were being used in conjunction with two film cassettes. This would require that, after exposure of the first lateral side of the film was complete for each cassette, both cassettes would then be removed from the machine, taken to a darkroom where the take-up reels were turned over and re-inserted into the cassette in place of the supply reel and the film path re-threaded and the cassettes returned to the machine for the exposure of the remaining lateral half of each film.
The use of a bi-directional film transport and a cassette configured according to the present invention would, after the first pass of the film but before the supply reels were depleted, allow each cassette to be removed from its respective cassette chamber and rotated about its axis of symmetry and once again re-inserted into its original cassette chamber so that the remaining lateral portion of the film could be exposed through the other exposure window in the film cassette. It should be noted that it is not necessary that the cassette be returned to its original chamber; that is, just the normal practice.